1. Technical Field
The present invention relates to an electro-optical device, such as a liquid crystal device, and an electronic apparatus having the electro-optical device, such as a liquid crystal projector.
2. Related Art
In an electro-optical device, a plurality of external circuit connection terminals are disposed along one edge of a substrate on which display electrodes, such as pixel electrodes, and a circuit unit, such as a data line driving circuit and a scanning line driving circuit for driving the display electrodes, are provided. On the substrate, a plurality of signal lines through which a plurality of different kinds of signal are supplied from the plurality of external circuit connection terminals to the circuit unit, such as the data line driving circuit and the scanning line driving circuit, are further provided.
For the signal lines, for example, JP-A-2002-229061 discloses a redundant wiring structure, in which additional wiring lines are formed in addition to original wiring lines by using the same layer as a conductive layer within pixels, thereby reducing the resistances of wiring lines without increasing the number of manufacturing processes.
However, since signal lines on which different kinds of signal run are patterned so that they do not overlap one another on a substrate in plan view, there is a limit to how much these signal lines are finely patterned on a single plane to narrow each gap between adjacent lines. For this reason, there is an intrinsic limitation in reducing area required for signal line layout, which makes it hard to miniaturize electro-optical devices. Further, as the electro-optical device becomes smaller, the gap between the signal lines becomes narrower. As a result, a problem occurs where interference between different kinds of signal supplied to the adjacent wiring lines increases. In particular, noises are generated in image signals due to, for example, a clock signal having a high frequency so as to operate the data line driving circuit or the like.
An advantage of some aspects of the invention is that it provides an electro-optical device, in which the size of a substrate can be reduced and high-quality images can be displayed by suppressing an effect of noises with respect to image signals, and an electronic apparatus having the electro-optical device.
According to a first aspect of the invention, an electro-optical device includes: a substrate; a plurality of pixels provided in a pixel region on the substrate; peripheral circuits that are provided in a peripheral region surrounding the pixel region, the peripheral circuits being for controlling the plurality of pixels; a plurality of signal lines that supply signals for controlling the peripheral circuits, that at least partially overlap each other in the peripheral region, and that are formed in a plurality of different conductive layers with interlayer insulating layers interposed therebetween; and a shielding layer that is provided between layers where the plurality of signal lines overlap each other, so as to overlap the plurality of signal lines.
In the electro-optical device described above, while the electro-optical device operates, for example, image signals, clock signals, various control signals, or power signals are supplied from an external circuit to the plurality of signal lines and the peripheral circuits through external circuit connection terminals. The plurality of signal lines and the peripheral circuits are provided in the peripheral region surrounding the pixel region on the substrate. Here, the ‘peripheral circuits’ according to the invention mean various circuits, which are provided or attached on the substrate, such as a scanning line driving circuit or a data line driving circuit for controlling or driving scanning lines or data lines electrically connected to pixels. For example, the data line driving circuit causes the image signals to be supplied to corresponding pixels through the data lines. At the same time, the scanning line driving circuit causes scanning signals to be supplied to corresponding pixels through the scanning lines. For example, a pixel-switching thin film transistor (hereinafter, referred to as ‘pixel-switching TFT’) provided for each pixel has a gate connected to a scanning line and serves to selectively supply an image signal to a pixel electrode according to the scanning signal. Thus, active-matrix driving becomes possible by driving electro-optical materials, such as liquid crystal, interposed between pixel electrodes and counter electrodes for each pixel. Further, a method of driving the electro-optical device is not limited to the active-matrix driving method. For example, various driving methods, such as a passive-matrix driving method or a segment driving method, can be used.
In the invention, the plurality of signal lines is formed on the plurality of different conductive layers with the interlayer insulating layers interposed therebetween, respectively. In addition, the plurality of signal lines at least partially overlap each other in the peripheral region, in plan view above the substrate. Accordingly, it is possible to dispose a large number of signal lines within a predetermined region of the substrate, as viewed from the normal direction of the substrate, such that the signal lines are not short-circuited by each other. In other words, it is possible to dispose a larger number of signal lines while making the width of each wiring line large. Thus, a pixel region can be made large, and at the same time, it is possible to reduce the size of the substrate by reducing the peripheral region. As a result, the entire liquid crystal device can be made small.
Further, in the invention, the plurality of signal lines is formed on different conductive layers among the plurality of conductive layers, respectively, according to the signal type, for example. Here, the ‘signal type’ means properties of a signal, such as a frequency of a signal or a level of a potential. For example, among the plurality of signal lines, signal lines through which signals having frequencies higher than a predetermined frequency are supplied are formed by using one conductive layer for high-frequency signal lines, and signal lines through which signals having frequencies lower than the predetermined frequency are supplied are formed by using one conductive layer for low-frequency signal lines different from that for the high-frequency signal lines.
Furthermore, in the invention, the shielding layer is provided between layers where the plurality of signal lines overlaps each other, so as to overlap the plurality of signal lines. That is, for the electrical shield between one signal line and another signal line among the plurality of signal lines, a shielding layer located between wiring portions, which overlap each other in plan view above the substrate on which the plurality of signal lines is formed, is included. Accordingly, it is possible to reduce electrical noises, which are generated on the one signal line and another signal line due to opposite signals, by means of the shielding layer. Here, the ‘shielding layer’ according to the invention means a layer having an electrical shielding function, such as conductivity. In addition, the ‘shielding layer’ may be an additional signal line located between one signal line and another signal line among the plurality of signal lines. That is, the invention includes a case, in which one of the plurality of conductive layers and the shielding layer are commonly used, and a case in which the shielding layer and one of the plurality of signal lines are commonly used. As a result, electrical noises, which are generated due to, for example, a clock signal for a data line driving circuit having high frequency as compared to image signals and affect the image signals, are reduced, which makes it possible to display high-quality images.
As described above, according to the electro-optical device of the invention, the size of the substrate can be reduced, which makes it possible to reduce the size of the electro-optical device. Further, since the electrical interference between different kinds of signal can be reduced, high-quality images can be displayed.
Further, in the above-mentioned aspect, the electro-optical device may further include a plurality of data lines and a plurality of scanning lines that are provided in the pixel region on the substrate so as to cross each other. In addition, preferably, the pixels are provided to correspond to intersections between the data lines and the scanning lines and each of the pixels includes a storage capacitor formed by sequentially stacking a lower electrode, a dielectric layer, and an upper electrode on the substrate, and each of the plurality of conductive layers and the shielding layer are the same layer as any one of the conductive layers forming the data lines, the lower electrodes, and the upper electrodes, respectively.
In the invention, each of the plurality of conductive layers and the shielding layer are the same layer as any one of the conductive layers forming the data lines, the lower electrodes, and the upper electrodes, respectively. Here, the ‘same layer’ means layers simultaneously formed during a manufacturing process, that is, the same kinds of layer. Basically, the ‘same layer’ does not necessarily extend as one layer, but includes separated parts of the one layer. Accordingly, the plurality of signal lines and the shielding layer can be formed at the same time as the data lines, the lower electrodes, or the upper electrodes are formed. That is, the plurality of signal lines and the shielding layer can be formed by using a plurality of conductive layers without causing the manufacturing process to be complicated.
In addition, due to the storage capacitor, the potential holding characteristic in a pixel electrode included in a pixel is improved and high-contrast display can be performed.
Furthermore, in the electro-optical device according to the abovementioned aspect, preferably, the plurality of signal lines is formed by using the conductive layers having different predetermined frequencies from each other.
In the invention, among the plurality of signal lines, for example, signal lines through which signals having frequencies higher than a predetermined frequency are supplied are formed by using one conductive layer for high-frequency signal lines, and signal lines through which signals having frequencies lower than the predetermined frequency are supplied are formed by using one conductive layer for low-frequency signal lines different from that for the high-frequency signal lines. For example, signal lines through which enable signals, clock signals, or the like for driving a data line driving circuit are supplied are formed as the high-frequency signal lines. On the other hand, for example, signal lines through which clock signals for driving a scanning line driving circuit are supplied, signal lines through which various control signals for controlling operations of peripheral circuits, such as the data line driving circuit or the scanning line driving circuit, are supplied, or signal lines for supplying image signals therethrough, that is, image signal lines are formed as the low-frequency signal lines. In addition, signal lines through which constant-potential or fixed-potential signals are supplied may be formed as the low-frequency signal lines. Accordingly, in the present embodiment, the shielding layer is located between layers in which the high-frequency signal lines and the low-frequency signal lines overlap each other, in plan view above the substrate. As a result, electrical effects of high-frequency signals, such as clock signals for driving the data line driving circuit, with respect to low-frequency signals, such as image signals, can be reduced. In other words, electrical interference between the low-frequency and high-frequency signals can be reduced. Thus, high-quality images can be displayed.
Furthermore, in the electro-optical device in which the plurality of signal lines is formed by using the conductive layers having different predetermined frequency ranges from each other, the plurality of signal lines includes first-frequency signal lines through which signals having a first frequency are supplied and second-frequency signal lines through which signals having a second frequency lower than the first frequency are supplied, and the first-frequency signal lines, the shielding layer, and the second-frequency signal lines are sequentially stacked in this order on the substrate with interlayer insulating layers interposed therebetween.
In this case, the first-frequency signal lines, the shielding layer, and the second-frequency signal lines are stacked in this order on the substrate with the interlayer insulating layers interposed therebetween. That is, for example, image signal lines for supplying image signals therethrough are formed as the second-frequency signal lines so as to be close to a surface of the stacked structure. Accordingly, it is possible to provide less contact holes required to electrically connect the second-frequency signal lines with the external circuit connection terminals formed in the vicinity of the surface of the stacked structure. As a result, the resistances of the second-frequency signal lines can be reduced. On the other hand, signal lines through which, for example, clock signals for driving peripheral circuits are supplied, are formed as the first-frequency signal lines so as to be close to the substrate in the stacked structure. In general, TFTs or the like, which are included in the peripheral circuits, are also formed to be close to the substrate. Accordingly, it is possible to reduce the number of contact holes between the first-frequency signal lines and the peripheral circuits. As a result, the first-frequency signal lines and the peripheral circuits can be easily connected to each other.
Furthermore, in the electro-optical device in which the plurality of signal lines is formed by using the conductive layers having different predetermined frequency ranges from each other, the plurality of signal lines includes first-frequency signal lines through which signals having a first frequency are supplied and second-frequency signal lines through which signals having a second frequency lower than the first frequency are supplied, and the second-frequency signal lines, the shielding layer, and the first-frequency signal lines are sequentially stacked in this order on the substrate with interlayer insulating layers interposed therebetween.
In this case, the second-frequency signal lines, the shielding layer, and the first-frequency signal lines are stacked on the substrate in this order with the interlayer insulating layers interposed therebetween. That is, signal lines through which, for example, clock signals for driving peripheral circuits are supplied, are formed as the first-frequency signal lines so as to be close to the surface of the stacked structure. Thus, it is possible to dissipate or eliminate heat, which is generated from the first-frequency signal lines because the frequencies of the first-frequency signal lines are high, through the surface of the stacked structure. That is, it is possible to easily prevent the first-frequency signal lines from being overheated.
Furthermore, in the electro-optical device including the first-frequency signal lines and the second-frequency signal lines, preferably, the shielding layer serves as a constant-potential wiring line through which a predetermined electric potential is supplied.
In this case, since the constant-potential wiring line serves as a shielding layer, it is possible to reduce the electrical interference between the different kinds of signal without causing the manufacturing process to be complicated, thereby displaying high-quality images. Further, the shielding layer may serve as a wiring line having a predetermined potential, through which a predetermined-potential signal whose electric potential changes to a predetermined electric potential every predetermined period, for example, the electric potential is inverted every predetermined period is supplied. Even in this case, since the electric potential of the signal is constant at each predetermined time, it is possible to reliably reduce the electrical interference in the same manner as described above.
Furthermore, in the electro-optical device in which the constant-potential wiring line serves as the shielding layer, preferably, the width of the constant-potential wiring line is at least partially larger than that of at least one of the first-frequency signal line and the second-frequency signal line, in plan view above the substrate.
In this case, since the width of the constant-potential wiring line is at least Partially larger than that of at least one of the first-frequency signal line and the second-frequency signal line, in plan view above the substrate, the constant-potential wiring line can reliably serve as the shielding layer so that the electrical interference between the first-frequency signal line and the second-frequency signal line can be reduced. In addition, since the width of the constant-potential wiring line is large, the resistance of the constant-potential wiring line can be reduced. Accordingly, due to the constant-potential wiring line, it is possible to supply stable constant-potential signals or stable constant-potential power to the peripheral circuits.
Furthermore, in the electro-optical device in which the constant-potential wiring line serves as the shielding layer, preferably, the width of the constant-potential wiring line is at least partially smaller than that of at least one of the first-frequency signal line and the second-frequency signal line, in plan view above the substrate.
In this case, it is possible to reduce a capacitance formed by the constant-potential wiring line, the interlayer insulating layer, and the first-frequency signal line or the second-frequency signal line, that is, it is possible to reduce wiring capacitance. Thus, it is possible to prevent the electric potential of the constant-potential signal from fluctuating due to effects of the first-frequency signal line and the second-frequency signal line. That is, it is possible to prevent electrical noises, which are generated due to the first-frequency signal line or the second-frequency signal line, from affecting image signals through constant-potential signals, such as constant-potential power.
Furthermore, in the electro-optical device in which the width of the constant-potential wiring line is smaller than that of at least one of the first-frequency signal line and the second-frequency signal line, preferably, the predetermined electric potential is a power supply potential having a first electric potential and a second electric potential lower than the first potential, the constant-potential wiring line includes a first-potential power line through which the first electric potential is supplied and a second-potential power line through which the second electric potential is supplied, the width of the constant-potential wiring line is at least partially smaller than any one of the first-frequency signal line and the second-frequency signal line, and the first-potential power line and the second-potential power line are disposed to be at least partially parallel to each other and to overlap the first-frequency signal line and the second-frequency signal line, respectively, in plan view above the substrate.
In this case, the first-potential power line and the second-potential power line are disposed to be at least partially parallel to each other and to overlap the first-frequency signal line and the second-frequency signal line, respectively, in plan view above the substrate. Accordingly, electrical noises between the first-frequency signal line and the second-frequency signal line are reduced by the first-potential power line and the second-potential power line.
In addition, in the case when the first-potential power line is provided between one first-frequency signal line and one second-frequency signal line and the second-potential power line is provided between another first-frequency signal line and another second-frequency signal line, an electrical effect between one first-frequency signal line and one second-frequency signal line is different from that between another first-frequency signal line and another second-frequency signal line. However, in the invention since the first-potential power line and the second-potential power line overlap the first-frequency signal mine and the second-frequency signal line, respectively, it is possible to obtain almost uniform shielding effects.
Furthermore, in the above-mentioned aspect, the electro-optical device may further include a relay layer that is formed by using the same layer as the shielding layer so as to electrically relay-connect upper signal lines of the plurality of signal lines with lower peripheral circuits of the peripheral circuits, the upper signal lines being formed above the shielding layer and the lower peripheral circuits being formed below the shielding layer.
In the invention, the upper signal lines are electrically connected to the lower peripheral circuits through the relay layer. That is, the upper signal lines and the relay layer are electrically connected to each other through contact holes provided in an interlayer insulating layer located between the upper signal lines and the relay layer, and the relay layer and the lower peripheral circuits are electrically connected to each other through contact holes provided in an interlayer insulating layer located between the relay layer and the lower peripheral circuits. Thus, it can be prevented from becoming difficult to connect each of the upper signal lines with each of the lower peripheral circuits through one contact hole, due to the large distance between layers forming the upper signal lines and the lower peripheral circuits. Further, since the relay line is formed by using the same layer as the shielding layer, the stacked structure and the manufacturing process do not become complicated.
Furthermore, in the above-mentioned aspect, the electro-optical device may further include a plurality of external circuit connection terminals that are electrically connected to the plurality of signal lines and the shielding layer, respectively, and are disposed in the peripheral region on the substrate. In addition, preferably, the shielding layer at least partially overlaps the signal lines electrically connected to the external circuit connection terminals adjacent to the corresponding external circuit connection terminals electrically connected to the shielding layer.
In the invention, the shielding layer at least partially overlaps the signal lines electrically connected to the external circuit connection terminals adjacent to the corresponding external circuit connection terminals electrically connected to the shielding layer. Accordingly, the shielding layer can exist even in a region where the plurality of signal lines are electrically connected to the external circuit connection terminals. As a result, it is further possible to reliably reduce the electrical interference between the plurality of signal lines that is formed on different conductive layers with interlayer insulating layers interposed therebetween.
According to another aspect of the invention, there is provided an electronic apparatus including the electro-optical device described above.
Since the electronic apparatus of the invention is configured to have the above-described electro-optical device of the invention, various electronic apparatuses, such as a projection type display device, a mobile phone, an electronic note, a word processor, a view finder type or monitor direct view type video tape recorder, a workstation, a video phone, a POS terminal, or a touch panel, which are capable of displaying high-quality images, can be implemented. Further, an electrophoresis device, such as an electronic paper, can be implemented by using the electronic apparatus of the invention.
Such effects and other advantages of the invention will be apparent from the following embodiments to be described.